Skywatch for the week of June 29, 2020
Mon June 29, 2020 Planet Symbols
Some star charts locate the positions of the moving planets, often using a symbol instead of the actual name. Each symbol is based on some aspect of that planet. Mercury, the messenger of the gods, has a walking stick symbol with two snakes wrapped around it (Yeah, that’d make me walk faster too.) A circle on a letter t makes a hand mirror - that’s for beautiful Venus. Mars, god of war, is symbolized by a shield and a spear. A stylized lightning bolt is the symbol for Jupiter, ruler of the sky. Saturn, god of the harvest, has a scythe. For Uranus, it looks like somebody jammed a Mars symbol onto a sun symbol; it’s probably got something to do with sex, but this isn’t that kind of a program so let’s move on. The moon’s symbol is the best, it looks like a crescent moon, while the sun is a dot inside a circle, like a drawing of an orbit around a star. Neptune is the king of the sea, so he bears a trident; and Pluto's is "P" and "L" combined. Can we talk about Pluto as a planet? Well, it’s got a symbol, so, yes!
Tue June 30, 2020 TUNGUSKA
A few years ago, an early morning fireball lit up the sky over Chelyabinsk, Russia. Shock waves from the impact shattered windows, injuring over a thousand people. Now this wasn’t the first time such a thing had happened. A hundred and ten years ago, something really big blew up in the atmosphere above the Tunguska region in Siberia. Reports from June 30th, 1908 sound a lot like the Chelyabinsk event. A brilliant blue light, like a second sun, flashed across the early morning sky. This was followed by a sonic shock wave that broke windows, killed wildlife, knocked people to the ground, and shook the earth. The Chelyabinsk impactor was a rock over fifty feet across. It came in at about 40,000 miles an hour – slow for a meteor – and it broke apart about ten to 15 miles above the surface. The total energy of the blast was roughly equal to a dozen or more atomic bombs. The Tunguska blast was at least five hundred times more powerful.
Wed Jul 1, 2020 FULL MOON HANGS LOW
All full moons rise at sunset and set at sunrise. So full moons are at their highest around the midnight hour (or 1 am, if you throw in daylight savings time.) But even though it’s at its highest then, July’s full moon isn’t very high. You see, full moons are directly opposite the sun. So they occupy the part of the sky where the sun will be found six months later. Half a year from now it will be winter, and the sun’s path in winter is very low; even at noon it’s not far off the south horizon. In summer the full moon is at the spot where the sun is in winter. So the summer’s full moon mimics the sun’s wintertime path. This also means that full moons in winter can reach the top of the sky at midnight, mimicking the sun’s path in summertime. So this month’s full moon won’t get very far above the horizon, and will be at a convenient altitude for us to admire it, just above the treetops, low in the southern sky at the midnight hour. Check out the full moon this weekend.
Thu Jul 2, 2020 EARTH AT APHELION
On Saturday the earth reaches aphelion – that’s the point in our planet’s slightly elliptical orbit where it’s farthest from the sun. On average, we're about 93 million miles from the sun, but right now we are roughly 94 and a half million miles out. So how come we're having summer? Well, not everyone on earth is experiencing summer; winter has just begun for folks south of the equator. Our seasons aren't caused by any variation in the earth-sun distance; after all, that extra million and a half miles only makes for a tiny 2% difference. Temperature changes occur because our planet is tilted over a little, about 23 and a half degrees, from straight up and down. During summer in the northern hemisphere, the top half of earth leans inward, which puts the sun higher in our sky, and causes summer; in the winter the top half of earth leans away from the sun, putting it lower in our sky, which cools things down.
Fri Jul 3, 2020 JULY FULL MOON
The moon is full tonight and tomorrow. Because thunderstorms are common in July, this full moon is often called the Thunder moon. According to the Sioux Indians, this is the Moon When the Wild Cherries Are Ripe. To the Winnebago, it is the Corn-Ripening Moon, and to the Kiowas, it is the Moon of Deer Horns Dropping Off. To the Omaha Indians, however, this is the Moon When the Buffalo Bellow. In ancient China, this was the Hungry Ghost Moon, named for departed souls who had left no descendants, and who according to legend caused drought, famine, fire or other disasters. In medieval times this was the Hay Moon or the Mead Moon, named for the elixir from the meadows of Briton and Europe. After this full moon came the first harvests from the fields and the pagan festival of Lughnasaid. Lughnasaid was later adopted by early Christians and became the celebration of Lammas, or “loaf mass,” in thanksgiving for the first fruits of the farmer’s labor.